1. Field of the Invention
The present invention relates to a carburetor for use with an internal combustion engine, and more particularly to such a carburetor which has pivotally mounted venturi plates and is provided with improved elements for discharging fuel into a venturi defined thereby and for coordinating the flow of fuel to be discharged with the position of the plates so that the carburetor provides desired air-fuel mixture ratio through the entire range of air flow required by the engine.
2. Description of the Prior Art
Carburetors having a variable venturi are well known. A carburetor of this type is disclosed in U.S. Pat. No. 3,752,451 to Kendig issued on Aug. 24, 1973, and hereinafter referred to as the "Kendig carburetor". The instant carburetor developed from the Kendig carburetor and efforts to improve its performance.
The Kendig carburetor is characterized by having a housing defining a rectangular mixing passage provided with a throttle at its downstream end, a pair of venturi plates at its upstream end, and a fixed fuel spray bar extending centrally across the passage between these ends. The plates pivot about individual axes adjacent to the walls of the passage toward its upstream end. When in a closed position, the plates extend normally to the passage upstream of the bar with their distal ends engaged at a point substantially upstream of the bar. As the plates pivot from the closed position to an open position they define a venturi between their distal ends which initially is above the bar but moves past it as the plates pivot downwardly to open.
The Kendig carburetor is further characterized by a system for metering fuel from a supply chamber in the housing to orifices in the bar which open into the passage. This system includes a pickup arm which pivots about an axis coincident with the bar. The pivotal movement of the arm is coordinated with pivotal movements of the plates by a train of gears. The arm has a conduit therein between its distal end and the bar. The conduit terminates at the distal end in an opening which moves over a stationary arcuate, concave metering ramp as the arm moves pivotally. The spacing of the ramp from the distal end varies with this movement thus variably restricting the flow of fuel to the orifices with the intention of providing a substantially constant air-fuel mixture ratio.
While the Kendig carburetor constituted a remarkable step forward in the art, it nevertheless has certain problems which the present invention has sought to overcome.